The importance of thiamine-dependent enzymes to the in vivo production of carcinogenic hydroxamic acids will be determined. Research to data has demonstrated that some such enzymes are capable of converting aromatic nitroso compounds to the corresponding hydroxamic acids. Mammalian enzymes such as pyruvate dehydrogenase and transketolase will be incubated with selected aromatic nitroso compounds and the extent of hydroxamic acid production then determined. Employing radiolabeled nitroso compounds, the investigator will determine if similar conversions occur in tissue homogenates and isolated organs. The results of this research project should enable scientists to assess the possible contribution of this process to the induction of neoplasms.